This invention relates to dehydrodidemnin B and, in particular, to the isolation of dehydrodidemnin B, a cyclic depsipeptide, from a tunicate of the Ascidiacea class. This novel compound has been shown to have antiviral, antitumoral and cytotoxic activities.
The didemnins form a class of cyclic depsipeptides which have been isolated from various species of the Trididemnum genus. They have been shown to have potent activity against viruses and tumor cells (Rinehart, Jr., et al., J. Am. Chem. Soc., 103, 1857-59 (1981). Didemnin B, up to now the most active compound of this class, has been shown to have potent immunosuppressive activity (Montgomery et al., Transplantation, 40, 49-56 (1985) and a more potent inhibition of binding of prolactin to human lymphocytes than other didemnin compounds (Montgomery. et al., Fed. Prac., 44, 634 (1987).
This invention provides a novel and more active compound of this class, unexpectedly isolated from the Mediterranean tunicate Alpidium albicans, namely dehydrodidemnin B (or xe2x80x9cDDBxe2x80x9d), having the formula: 
where R is hydrogen; and derivatives thereof with the same class of biological activity, i.e., where R is Acyl, Alkyl or Aryl.